Not having done it myself, I can only speculate, but I think it is one of those "UGLY" jobs.
By taking the hose off at the valve body and removing the hose from the outboard end of the pipe you 'might' be able to snake the whole thing out the bottom of the boom by the pivot. Kind of depends on how the hard line is held in place. I think mine uses a clamp plate with a bolt through it. Odds are there is a nut on that on the inside under the boom cylinder.
You might save yourself a lot of frustration by just laying the boom and stick out straight, block it up and pull the boom cylinder. I had to replace the boom cylinder once and it was not that bad of a job. Not easy like a bucket cylinder, but I got it done by myself. Once the cylinder is out of the way, you will be able to make the needed repairs much easier.
After all that work, I would have to seriously consider replacing all the hoses in that part of the boom. Especially if they have some age on them.
Best of luck. Take pictures to aid in re-assembly and post them here to help others in the future.